The invention relates to a peristaltic pump adapted to operate simultaneously on two lines.
As known, peristaltic pumps comprise a rotatable head provided with rollers adapted to compress at lease one fluid conveyance line made of flexible material, such as PVC, silicon, or polyurethane, against portions of a cylindrical resting surface in the fixed body of the pump. For efficient operation of the pump, the rollers exert pressure which provides perfect occlusion of the flexible line, and the pumps are provided with critical means of adjustment.
Typically, use is made of these pumps in the medical field, for example for infusing drugs, or in extracorporeal blood circuits. It often occurs that a peristaltic pump has to operate simultaneously on two lines which must convey different flows of fluid in a precisely determined ratio, as required for example in the case of the simultaneous conveyance of blood in one line and of anticoagulant liquid in the other. The required ratio between the flow rates of the two fluids is achieved by an appropriate choice of the passage areas of the respective lines. However, an operator having a known type of peristaltic pump available encounters serious limitations. In known pumps, the two portions of cylindrical resting surfaces of the two lines have the same radius of curvature and therefore it is necessary to employ lines with different passage areas but having the same wall thickness to obtain their perfect occlusion.
The provision of such lines is always difficult, and it is thus an aim of the present invention to provide a peristaltic pump which is adapted to efficiently operate simultaneously on two lines, without requiring that the two lines necessarily have the same wall thickness.